Laser Machining a Transparent Workpiece

Abstract

The invention relates to a method for machining a transparent workpiece (4) by generating non-linear absorption of laser radiation in a laser beam focus located in a volume of the workpiece (4). The object of the invention is that of providing a method of improved precision and quality, and a corresponding device, for laser machining of workpieces. In particular, it is also intended for it to be possible for workpieces made of composite materials or of other special materials, such as filter glass, to be machined at an improved level of quality. For this purpose, the method according to the invention comprises the following steps:spectroscopic measurement of the linear absorption of the laser radiation in the workpiece (4),selecting a working wavelength at which the linear absorption is low, andmachining the workpiece (4) by means of the application laser radiation at the working wavelength. The invention furthermore relates to a corresponding device for machining a transparent workpiece (4).

1 . A method for machining a transparent workpiece by generating non-linear absorption of laser radiation in a laser beam focus located in a volume of the workpiece, the method comprising:
 spectroscopic measurement of the linear absorption of the laser radiation in the workpiece using a laser that is tunable with respect to a wavelength of the laser radiation;   selecting a working wavelength at which the linear absorption is low; and   machining, using the laser, the workpiece by means of the application of laser radiation at the working wavelength.   
     
     
         2 . The method of  claim 1 , wherein the working wavelength is selected in accordance with the stipulation that, at the working wavelength, the linear absorption in the laser beam direction is less than 20% per centimeter. 
     
     
         3 . The method of  claim 1 , wherein the working wavelength is selected in accordance with the stipulation that, at the working wavelength, the linear absorption in the laser beam direction is less than 10% per centimeter. 
     
     
         4 . The method of  claim 1 , wherein the transmission curve resulting from the measurement of the linear absorption exhibits a minimum at the working wavelength. 
     
     
         5 . The method of  claim 1 , wherein during measurement of the workpiece, the intensity of the laser radiation remains below a threshold at which ionization processes occur in the volume of the workpiece. 
     
     
         6 . The method of  claim 1 , wherein the laser radiation is pulsed, and the pulse duration of the laser pulse is from 10 fs to 100 ps. 
     
     
         7 . The method of  claim 1 , wherein the working wavelength is selected in accordance with the secondary condition that the non-linear absorption should be as high as possible, at a harmonic of the working wavelength. 
     
     
         8 . The method of  claim 1 , wherein machining the workpiece comprises separating glass workpieces. 
     
     
         9 . The method of  claim 8 , wherein the position of the laser focus is guided, during the machining, between two or more connected glass workpieces, along a separation plane or a predetermined breaking point. 
     
     
         10 . A device for machining a transparent workpiece, the device comprising
 a laser that emits a laser beam at an adjustable working wavelength;   coupling optics that couples the laser beam into a volume of the workpiece and focusses the laser beam in a laser beam focus located in the volume of the workpiece;   a measuring device that measures a linear absorption of the laser radiation in the workpiece;   a controller coupled to the laser, the measuring device and the coupling optics, wherein the controller is designed to set the working wavelength to a value at which the linear absorption is low, and to vary the position of the laser beam focus during the machining of the workpiece.   
     
     
         11 . The device of  claim 10 , wherein during the machining, the laser emits the laser beam at an intensity at which non-linear absorption, in particular ionization, occurs in the laser beam focus.